METCALFE: Acidified oceans seek equilibrium

Exploring the causes and consequences of our carbon addiction in Nova Scotia

A coral reef. JERRY REID (USFWS)

The buildup of C02 in our atmosphere is the defining issue of our time, caused by the fundamental workings of our civilization and resulting in the catastrophic warming of our planet. But while our eyes are rightly fixed on this climbing thermometer, another consequence of rising C02 often escapes our gaze.

We tend only to hear about ocean acidification in reference to dying reefs, but this acidity could, in time, have considerably more casualties than just coral. To understand its science I travelled to Dalhousie University and the office of Dr. Helmuth Thomas, a marine biogeochemist who has been researching the carbon cycle of coastal oceans for almost three decades.

As he explained, our oceans and atmosphere always strive for equilibrium. If C02 concentrations rise in our atmosphere, the oceans will absorb their fair share; if concentrations drop, however, our oceans will release their stored C02 in equal measure. So where our atmosphere leads, the oceans will follow. Unfortunately, this balancing act comes with some problematic chemistry.

Back to school

We measure acids and bases on what’s called the pH scale. In case you’re rusty from high school chemistry, a scale which ranges from the strongest bases at pH 14 to the strongest acids at pH 1, with pH 7 representing the chemical neutrality which divides them. Where on this scale water falls depends on the substances dissolved in it.

Our oceans are naturally basic, Helmuth told me, kept that way by the weathering of rocks and the liberation of their carbonates, keeping our oceans at a healthy pH and supplying countless marine species with the materials necessary for shell formation. Dissolved C02, however, yields hydrogen ions which compete with marine life for these carbonates, acidifying our oceans and disenfranchising several shelled species.

According to the National Oceanic and Atmospheric Administration in the United States, our oceans’ surface pH has dropped from 8.2 at the dawn of the Industrial Revolution to 8.1, which sounds insignificant until put into context. The pH scale is logarithmic, meaning a jump of 0.1 amounts to 30 per cent greater ocean acidity. In the chemistry lab, Helmuth said, you routinely explore the entire pH scale but in a system as enormous and stable as our oceans, a change of this magnitude is hugely consequential.

“For the ecological system in particular, this can already be a very dramatic change,” he said.

Them with shells

Calcifying organisms are those who combine free-floating calcium and carbonate to create — you guessed it — calcium carbonate, an essential ingredient in shell formation. These marvellous structures are as varied as the organisms who employ them, from the stunning shapes of coral reefs to the iconic exteriors of commercial mussels. Even algae make use of these oceanic carbonates, themselves essential to marine ecology.

“What’s established very well is that, as the oceans acidify, the formation of these calcium carbonate structures becomes a problem,” said Helmuth.

As our oceans are robbed of these carbonates by invading C02, calcifying organisms are increasingly short-changed. Helmuth told me the thinning and general damage to overall shell structure has already been observed in a variety of marine species.

Coral reefs, algae and other carbonate-dependent creatures play fundamental roles in marine ecology, their decline or disappearance of great consequence throughout the food chain. It seems to me very nearly nothing is safe from ocean acidification, our seafood-loving selves included.

Exactly what this will mean for the oceans of tomorrow, Helmuth declined to guess. A great many predications have been made concerning the outcomes of ocean acidification, overwhelmingly negative ones, but each seems to point in a different direction. Ocean ecology is so maddeningly complex that it’s perhaps beyond the reach of accurate modelling, at least for the time being.

The Scary Part

“It’s not reversible,” Helmuth told me near the beginning of our conversation. “You cannot undo this change, which I think is the largest problem.”

This was far and away the most frightening revelation of the interview, as I’m sure you can appreciate. While hatcheries and watersheds across Atlantic Canada can manage ocean acidification with the application of agricultural grade lime, we couldn’t possibly treat the world’s bays or oceans in the same way. There exists no silver bullet.

Helmuth reminded me also of our global conveyor belt — interconnected currents of water which pull our oceans in an elaborate circuit around the globe, travelling partly at the surface and partly in the depths. A full circuit takes 1,500 years, he told me, so while ocean acidification is presently affecting only the surface of our oceans, in time it will be dragged along the ocean floor as the belt continues, out of reach for centuries.

But while ocean acidification is and will continue to make itself felt in marine ecology, there is of course a solution in spite of Helmuth’s early remark, one so obvious it’s a travesty we didn’t start decades ago: We need to stop emitting C02.

Our emissions have proven themselves stubborn in past decades due to market forces, bad politics and the deviousness of misinformation, but for the first time these obstacles have met their rival. Recent revolutions in power generation, energy efficiency, agriculture, public awareness and political will have the potential not only to cap our C02 emissions but even to remove them from the atmosphere. If this happens our oceans will follow suit, expelling what we’ve forced them to absorb and again becoming comfortably basic.

“Global warming and ocean acidification are two sides of the same coin,” explained Helmuth. “They’re twins.”

So while we’ve been presented with yet another crisis, we’re strangely fortunate it shares a solution with global warming, something already in dire need of fixing. In this context, ocean acidification is yet another reason to support the capping of emissions and our transition to a carbon-free economy, all the more important for us stewards of the Atlantic.

Zack Metcalfe is a freelance environmental journalist, author and writer of the Endangered Perspective. He operates out of Halifax.